Marriage to two women was an uncommon practice in ancient times, often pointing to complex and difficult life circumstances. An immediate and painful divide existed in Elkanah's home: one wife was blessed with children, while the other was left with empty arms.
The primary approach among commentators is that Hannah was Elkanah's first wife, initially living alone with him in their marriage [מלבי״ם, אלשיך]. When she realized she was unable to conceive, Hannah herself initiated bringing Peninnah into their home. She hoped that by doing so, she might be built up and blessed with children in her own right, following the historical examples of Sarah and Rachel [מלבי״ם, אלשיך, אהבת יהונתן, ביאור שטיינזלץ].
However, this heartbreaking sacrifice did not yield the desired result. Even though Peninnah entered the marriage later, she quickly bore children, while Hannah remained childless [מלבי״ם]. Furthermore, unlike the biblical mothers who viewed the children of their maidservants as their own, Peninnah acted with ingratitude. She claimed her children exclusively for herself, leaving Hannah completely empty-handed [אהבת יהונתן, אלשיך].
Interestingly, Hannah was not physically incapable of having children. She was naturally fit to be a mother, but God miraculously and intentionally withheld pregnancy from her [אברבנאל]. He did this because He deeply desires the prayers of the righteous. By preventing her from having children, God sought to awaken Hannah to pray from the very depths of her heart, ensuring that her eventual child would be born through divine will and a clear miracle [אלשיך, אברבנאל]. On the other hand, Peninnah was granted children through divine providence as a form of compensation. Because Elkanah loved Hannah more, God blessed the less favored wife with a growing family [רלב״ג מובא באברבנאל].
Despite the bitter dynamic between the two women, Peninnah possessed an underlying merit characteristic of righteous individuals. This supports the tradition that Peninnah's harsh provocations were actually done for the sake of heaven. Her true intention was to cause Hannah enough pain that she would finally turn and pour out her soul to God in prayer [אהבת יהונתן].
The reality of managing two such distinct households might also explain Elkanah's geographic origins, which imply two elevated locations. He may have settled Hannah and Peninnah on two separate hills that overlooked one another, dividing his time and his life between the two homes [אברבנאל].